The invention concerns apparatus for the detection and evaluation of process parameters arising during the remelting of an electrode to a metallic block in a vacuum are furnace.
During the remelting of electrodes into blocks various faults arise. The best-known of these faults are voids or pipes, `tree-rings`, segregations, white spots, `freckles`, non-metallic inclusions and structural disorders. Should one or more of these faults be discovered at certain locations, the whole block is usually thrown away, because the assumption is made that in addition to the discovered locations similar faults are also present at undiscovered positions. This conclusion is, however, often incorrect because the fault arose by a single disturbance of a process parameter which no longer arises again during the subsequent stages of melting. If the site of the fault that has occurred were known, then only the frequently very small faulty location of the block would require excision. The rest of the block could then still be wholly delivered for its proper purpose.
There is already known a process for regulating the course of melting away of self-consuming electrodes, wherein the instantaneous actual weight of the electrode as well as the electrical properties of the section between the electrode and the surface of the melt bath influence the regulation (DE-AS-1,934,218). Here not only are the electric data relating to the arc gap utilized in the regulation, but on this regulation a further regulation of the power input of a metallurgical furnace is superimposed. Thus one is concerned here with a regulation having several influencing parameters. A correlation of faults arising in the melting process to a defined site of the finished block is not possible with this process.
Furthermore, a process for the automation of the electrode melt processes is known, wherein the state of the melting process is determined according to a complex criterion, which takes into account the energy consumed, the harmonic content and fluctuations of the arc current, the spatial position of the electrodes and the temperature of the hottest zone of the delivery (D. A. Gitgarz: The Use of Microprocessors for the Control of Arc and Induction Melting Furnaces, Elektrie 35, 1981, pp. 545-547). A positional correlation of faults is not possible with this process either.